Outdoor water hydrants are useful for supplying potable water in various locations, such as parks, farms, railroad yards and various other outdoor settings. Because the water dispensed from such hydrants may be consumed by humans or animals, the water must be provided from the water source under sanitary conditions. Thus, care must be taken that the hydrant is sealed from the surrounding environment against leaks into the hydrant or water supply. If these outdoor hydrants are used with hoses, they are often fitted with vacuum breakers to prevent back flow of water from the environment through the hydrant which could contaminate the water supply. Furthermore, because these outdoor hydrants may be exposed to freezing temperatures, there is a potential for water in the hydrant to become frozen, where it may clog or damage the hydrant. To overcome this problem, valves used in outdoor hydrants are commonly buried in the ground below the level to which freezing temperatures may penetrate (i.e. below the frost line). Accordingly, the valve must be opened from above the ground, whereby water is provided to the surface through a riser pipe and an outlet of the hydrant.
Conventional outdoor hydrants have several drawbacks. For example, the external riser which connects the valve buried beneath the frost line to the outlet above the surface of the ground may be exposed to freezing temperatures, whereby water in the riser can freeze to either clog or damage the hydrant. To overcome this problem, water remaining in the riser after the valve is closed is often drained from the riser. This solution creates further problems, however. If the residual water from the riser is drained into the soil around the hydrant, a potential is created for “brown water” to enter the hydrant through drain holes, whereby fresh water may become contaminated on next use of the hydrant. If, instead, the residual water is drained to a reservoir below the frost line, this residual water is generally mixed with fresh water from the supply when the value is reopened. Because the fresh water is mixed with the old water as it is dispensed from the hydrant, it may take a long time, as much as a minute or more, to completely expel the old water from the hydrant.
Conventional systems which drain residual water to a reservoir typically utilize a venturi system to draw the water from the reservoir when the valve is reopened, whereby the flow of water from the water supply is used to entrain the stored, residual water and dispense it from the outlet. These venturi systems generally require a high velocity, low pressure flow for proper operation. This high velocity, low pressure flow is often in conflict with the requirements of the vacuum breaker system, which requires a minimum pressure threshold to function properly and which may restrict flow to a point where the venturi is ineffective. Still another drawback of conventional outdoor hydrants is that excavation is required to access and service wear parts of the hydrant which are located beneath the surface. The exposed riser is also susceptible to damage from above the surface, or when excavation is performed near the hydrant.
There is thus a need for an improved water hydrant which can be used to supply potable water under sanitary conditions while overcoming drawbacks of conventional water hydrants, such as those described above.